Question About Watts

[blesser13]

There a huge variety of low light plants that you can get for example, Anubias, Cryptocoryne aponogetifolia, Cryptocoryne x willisii 'lucens they ask low light. You could start with this here example of a low light tank My link

 

[morbes]

You do not use the equivalent value. They are 2x20 watt bulbs so your tank has 0.5 WPG.

That makes absolutely no sense to me. How is a 20w CFL only @ 1/4 the light of a 75w incandescent? Why does it matter how much it adds to my electric bill if it puts out more light? The tank is insanely brighter than it was when I had 2 40w incandescent bulbs in it before. But you are saying those two 40w bulbs was twice as much light as these? More electricity=more light period? Please explain.

I am curious to this answer as well. I am new to the hobby but just replaced my 1 puny 17 watt florescent bulb with 4x23 watt CFL (100 watt equivalent each). My tank is 45 gallons and 24 inches high. I would assume you would calculate off the "equivalence" because it does put out more light than a 23 watt bulb would. Can someone knowledgeable reply please?

 

[Mikaila31]

You do not use the equivalent value. They are 2x20 watt bulbs so your tank has 0.5 WPG.

That makes absolutely no sense to me. How is a 20w CFL only @ 1/4 the light of a 75w incandescent? Why does it matter how much it adds to my electric bill if it puts out more light? The tank is insanely brighter than it was when I had 2 40w incandescent bulbs in it before. But you are saying those two 40w bulbs was twice as much light as these? More electricity=more light period? Please explain.

Incandescent do not follow the WPG rule. I myself do not know of any rule for them and growing plants, because most people do not use them. They are horrible for growing plants period. The WPG rule was created with florescent T8 bulbs in mind, and can be varied a little for other types of florescent. Wattage is the amount of power it consumes not the amount of light it puts out. The 20 watt CFL puts out the same amount of light as the 75 watt incandescent, basically those 55 extra watts are wasted as heat, which is why incandescent bulbs are wasteful compared to energy saving ones. Fluorescent produce more light per watt and less heat. When you get into bulbs and lighting it can get really complicated. Wattage is only one measure of an bulb and it does not mean a whole lot. I can think of half a dozen other measurements that can be applied to a fluorescent. What it comes down to is your plants care about the amount of usable light emitted by a bulb, not the wattage, heat, or type.

More electricity defiantly does not mean more light period. I'm sure your familiar with LEDs. They can emit quite a lot of light using only a fraction of a watt. If you have ever run into a high powered LED that uses 'large' amounts of power like 1 or 3 watts, "bright" hardly describes them.